Prior arts and problems thereof will be described concerning an apparatus for discharging a mist which contains a perfume as an example of the above-mentioned chemicals.
In recent years when people are subjected to various stress, fragrance generators using an ultrasonic mist generator attract attention as products for giving people healing. They will become attractive products if various aromas c˜n be presented while switching them.
Generally, while an element with a piezo-electric effect or a magnetostrictive effect is used for an ultrasonic transducer used for the mist generator, there are element structures to be used, one has a cantilevered suspension structure, namely, one tip of the vibrator is fixed, and the other tip thereof is vibrated at high speed while contacting it to a liquid; and the other one has a structure in which the element is vibrated in a thickness direction while surroundings of the element being supported, like a disk type vibrator.
As an example of the former cantilevered suspension structure, a structure in which a liquid is retained in a liquid retaining material such as small a sponge, and the vibration point is contacted to the liquid retaining material to thereby generate the mist is disclosed in a fragrance generator of Japanese Published Examined Application Hei. 7-112491. Various aromas can be generated, if a plurality of liquid retaining materials for retaining various perfume liquids are prepared to make them contact with the vibration point.
In the case of the cantilevered suspension structure, however, since it is difficult to vibrate the vibration point at high frequency, particle diameters of the generated mists are apt to be large and uneven. The mists with large particle diameters disperse around the circumference of the apparatus without evaporating, thus causing a problem leading to contaminations.
Additionally, there are problems that an amount of atomization per unit time is small since the contact portion is small, production thereof is difficult since a contact mechanism portion between the tip of the ultrasonic transducer and the liquid retaining portion requires high accuracy, and the mechanism portion is easily degraded. For this reason, there are few examples commercialized as home use.
Meanwhile, an apparatus for generating the mist by ultrasonically vibrating the liquid at high speed while putting the disk type ultrasonic transducer in a liquid storage is disclosed, for example in an ultrasonic atomizing apparatus of Japanese Unexamined Patent Publication (Kokai) No. 2003-245580, and in a humidifier of Utility Model Registration No. 3100873, or the like. Since it is possible to vibrate the vibrator at a high frequency over 1 MHz, the particle diameters of the mists can be made extremely small. Considering applications to the fragrance generators, it will be an apparatus with excellent smell characteristics because of an easy evaporation of the perfume.
In the disk type ultrasonic transducer driven at the high frequency, however, the ultrasonic waves reflect on the surface of the element once the liquid stops existing in the plane of vibration, causing a problem that the ultrasonic transducer itself generates heat to increase a temperature thereof.
In the case of a piezoelectric device, if the temperature of the element exceeds a predetermined temperature, a piezoelectric polarization characteristic thereof will be degraded, or the element itself will be broken to be destroyed. Although it also depends on materials, the polarization is degraded when the element temperature is about 80 degrees Centigrade or more, and it may be destroyed about 150 degrees Centigrade or more. There are similar problems also in the element utilizing the magnetostrictive effect.
Hence, the ultrasonic transducer driven at a high frequency is commonly used in such a way that the sufficient liquids may always exist on the plane of vibration. In other words, since there is a risk that the ultrasonic transducer may be destroyed, the mist generator for atomizing a small amount of liquid by the ultrasonic waves with a high frequency has not been well studied so far in the field of household articles.
Many ultrasonic mist generators commercialized as home use now usually atomize water or one type of perfume-containing liquid. In addition, most of the systems atomize the liquid for atomization in a condition where it is sufficiently supplied on the ultrasonic transducer.
However, even when one type of aroma is discharged for a long time, people stops feeling the aroma shortly since they have smell adaptive characteristics, so that an expensive perfume becomes useless easily. When a perfume that is strong in physiological influence is used, there may also arise a problem which is not preferable on healthy.
Moreover, since the conventional ultrasonic mist generator is hard to be cleaned because of its structure, remaining perfume tends to contaminate the inside of the apparatus when using a perfume-containing liquid. It has hardly spread as a whole because of such a maintenance problem.
Hereinafter, it will be described that what kind of technical problems there are in the conventional mist generators that use the high frequency ultrasonic transducer using specific examples.
FIG. 28 is an exemplary example of the conventional home mist generator using an ultrasonic transducer. FIG. 28(A) is a sectional view and FIG. 28(B) is a top view. A cross section at the dashed line Sec in FIG. 28(B) corresponds to FIG. 28(A). In the same figure, reference numeral 13 is a liquid container, reference numeral 21 is a liquid storage, reference numeral 40 is an ultrasonic transducer, reference numeral 79 is an air blower mechanism, and symbol S is a liquid level sensor.
An operation thereof will be described briefly. In the same figure, a perfume-containing liquid Wa in the liquid container 13 flows into the liquid storage 21, and is kept at a water level of T1. T1 is decided by a position (height) of a liquid outlet 14 of the liquid container 13. When the liquid Wa in the liquid storage 21 is decreased, the liquid Wa is automatically supplied into the liquid storage 21 since air flows into the liquid container 13 from the liquid outlet 14. Thus, the water level is always kept at T1.
Operation of an ultrasonic transducer 40 will generate a liquid column AK1 from a liquid surface, and droplet dispersed liquids AK2 and atomized fine-particles ma will be generated from an upper part of AK1. Hereinafter, the atomized fine-particles will be expressed as mist. AK2 collides with a liquid dispersion preventing mechanism 49 and drops. The mist ma is discharged by the air blower mechanism 79 from a mist discharge port 59 of a mist discharge tube 58. An alternate long and short dash line Fg indicates an air current flow by the air blower mechanism.
When the liquid in the liquid container 13 becomes empty, a liquid level of the liquid storage 21 will drop. When the liquid level drops to T2, the liquid level sensor S will operate and driving power to the ultrasonic transducer 40 will be cut off. T2 is a water level with which a plane of vibration of the ultrasonic transducer 40 is fully filled, and is normally set to an upper point by about 1 cm from the plane of vibration. This is for preventing boil-dry of the ultrasonic transducer 40.
Next, the problems of the conventional mist generator shown in FIG. 28 will be described. A first problem is related to means for atomizing the liquid. Since the plane of vibration of the ultrasonic transducer 40 faces upwardly, the liquid column AK1 is generated vertically. A part of ultrasonic energy is consumed for pushing up the liquid.
For this reason, a rate for the ultrasonic energy to be used for atomization is small, thus causing less atomization efficiency. Additionally, since the liquid column AK1 tends to be high and the mist is generated from a wide range of an upper part of AK1, the mist discharge tube 58 must be high and large in capacity, causing the mist generator to tend to be large-scale.
Moreover, when the air flow generating means 79 is used in order to discharge the mist, a part of droplet dispersed liquids AK2-F will be carried together with the mist, causing a problem that the liquids are dispersed around the circumference from an opening 59 to contaminate it.
A second problem is related to means for changing an aroma type. In order to change the aroma type in a configuration shown in FIG. 28, it is necessary to replace the liquid in the liquid storage 21. However, a volume of the liquid storage 21 is large, and it is necessary to create a situation where the perfume-containing liquid Wa above T2 always exists in order to prevent that the ultrasonic transducer 40 falls in a boil-dry state, and thus even when the liquid container 13 is exchanged to a liquid container containing another perfume, the liquids before and after the exchange are mixed with each other in the liquid storage 21, making it difficult to switch the aroma at high speed and clearly.
A third problem is related to cleaning and maintenance. As described above, since the mist discharge tube 58 is large, the droplet dispersed liquids AK2 disperse in a wide range. For this reason, it is troublesome to clean the inside of the apparatus and its maintainability is poor. This is a serious problem as the home mist generator.
Moreover, in order to prevent degradation of the ultrasonic transducer 40 as described above, the liquid in the liquid storage 21 cannot be used up. Namely, even after the apparatus is used, the liquid storage 21 will be in a situation where the liquid always remains. When the perfume-containing liquid Wa is left as it is, it will cause perfume degradation and bacteria breeding. That is unsanitary and bad also for health rather than healing.
A fourth problem is related to the air flow generating means 79. Since the mists are only blown out of the opening 59 in a system using normal air blowing blades, it is visually uniform and insipid. Stage effects are unsatisfactory.
As described above, the ultrasonic mist generator for home use has less atomization efficiency, and does not primarily have a structure aiming at switching the aroma, so that it might not be used as an aroma switching apparatus. Naturally, it neither has a function for mixing aromas. Even when it is used as a single-aroma generator, there are maintenance problems, such as useless consumption of the perfumes, troublesome cleaning, or the like. Moreover, there are problems that the apparatus tends to be large-scale, and there is no function for increasing healing effects by producing the discharge of the mist.
[Patent Document 1] Japanese Published Examined Application Hei. 7-112491
[Patent Document 2] Japanese Unexamined Patent Publication (Kokai) No. 2003-245580
[Patent Document 3] Utility Model Registration No. 3100873
[Patent Document 4] Japanese Unexamined Patent Publication (Kokai) No. 2003-38646
[Patent Document 5] Japanese Unexamined Patent Publication (Kokai) No. 2003-266034
[Patent Document 6] Publication of Unexamined Utility Model Application No. Sho. 58-8034
[Patent Document 7] Publication of Unexamined Utility Model Application No. Hei. 2-104872
[Patent Document 8] Publication of Unexamined Utility Model Application No. Sho. 63-198933
[Patent Document 9] Japanese Unexamined Patent Publication (Kokai) No. Hei. 3-65264
[Patent Document 10] Japanese Unexamined Patent Publication (Kokai) No. Hei. 07-213968
[Patent Document 11] Japanese Unexamined Patent Publication (Kokai) No. 2002-200447